The invention relates to interior lighting systems for a passenger transportation vehicle such as an airplane, a ship, a bus, or a railcar and, in particular a dimmable LED reading light unit for such passenger transportation vehicle.
In passenger transportation vehicles, such as an airplane, a ship, a bus, or a railcar, halogen lights have been used as reading lights or seat lights. Due to their limited light yield and their comparably high power consumption, there is a tendency of replacing existing halogen lights by modern LED lights that have a higher light yield and lower power consumption.
However, in many cases it is not possible to adapt the existing power supply units in such passenger transportation vehicles, for example in airplanes, to the changed needs of LEDs that a replacement of a halogen light by a LED light brings with it. Such adaptation would be costly and cumbersome.
Further, the functionality of the light to be capable of being dimmed in order to emit light with a selected light intensity must be maintained.
Accordingly, it would be beneficial to provide a dimmable LED reading light unit having a high efficiency and being capable of replacing a conventional light unit. Further, it would be beneficial to provide a corresponding reliable method of operating dimmable LED reading light unit. Moreover, it would be beneficial to facilitate the replacement of a conventional light unit by a dimmable LED reading light unit as much as possible while replacing as few parts as possible and without changing the power supply unit and existing wiring.